This invention relates to rolling mills for reducing metal, and more particularly to apparatus for containing coolant liquid applied to the rolls of such mills. Typically, a mill as herein contemplated comprises upper and lower work rolls between which the metal to be reduced passes (e.g. in sheet or strip form), and upper and lower backup rolls respectively above and below (and in contact with) the upper and lower work rolls.
In an important specific sense, the invention is concerned with improvements in and/or modifications of the apparatus described in U.S. Pat. Nos. 3,994,151 and 4,061,010, the disclosures of which are incorporated herein by this reference. As in those patents, the invention will be particularly described as employed in the cold rolling of aluminum sheet or strip, the term "aluminum" being used herein to refer to aluminum-based alloys as well as pure aluminum metal. It will be appreciated, however, that the invention in its broader aspects is applicable to any type of rolling mill for reducing metal wherein coolant is applied to the mill rolls and wherein contact of the coolant with surfaces of the metal being reduced is to be avoided or minimized.
The aforementioned patents explain that, in rolling operations such as cold rolling of sheet aluminum, it is necessary to cool the mill rolls by applying thereto copious quantities of coolant liquid, typically also containing a lubricant. As the patents further explain, it is advantageous from an operational standpoint to use water as the coolant, or a water-based coolant/lubricant system. Metals such as aluminum, however, are subject to unacceptable surface staining if appreciable quantities of the water or water-based coolant come into and remain in contact with the surfaces of the reduced metal strip emerging from the mill.
The aforementioned patents describe coolant application and containment systems for preventing aqueous liquid coolant from falling and/or splashing on the strip surfaces as and after the strip emerges from the mill roll bite. Stated broadly, these systems include upper and lower coolant-applying spray heads respectively disposed to direct the coolant spray onto the surfaces of the upper and lower work rolls only on the exit side of the mill (the side from which the reduced metal strip emerges), and upper and lower casings or enclosures respectively surrounding the upper and lower spray heads and at least adjacent portions of the roll surfaces. The sprayed coolant collects in and is drained from the enclosures.
In one such arrangement shown in the patents, the upper enclosure has upper and lower horizontal edges extending in close but spaced relation to the upper backup and work roll surfaces so as to define therewith narrow gaps extending lengthwise of the rolls respectively above and below the upper spray head on the exit side of the mill. The directions of roll surface movement past the two gaps are both into the enclosure; and the interior of the enclosure is kept at subatmospheric pressure, to create constant inward flows of air through the gaps, for cooperating with the inwardly directed roll surface movement in preventing escape of coolant water from the enclosure. The vertical end walls of the enclosure, adjacent the ends of the rolls, may have edges conforming generally to (but spaced slightly from) the roll surfaces and may optionally bear spring-loaded rubbing seals. A similar enclosure may be provided for the lower spray head and the lower work and backup rolls.
Athough the arrangement just described offers significant advantages for coolant containment, it has been difficult to attain continuous trouble-free operation with embodiments of this system heretofore constructed, and the use of such embodiments has been attended with high maintenance costs. Particular problems have been encountered in achieving and maintaining a proper gap width, which is essential to satisfactory performance. In addition, the design of these prior embodiments of the system does not readily accommodate changes in roll diameter, as are commonly necessary in rolling mills. It would be desirable to provide coolant containment apparatus, generally in accordance with the aforementioned patents, affording ease of installation and maintenance, improved reliability, convenient adaptability to a practicable range of differing roll diameters, and enhanced protection of the rolled strip against stain-producing deposits of coolant liquid.